Chromatographic separation method

Abstract

A method for fractionating a solution into two or more fractions. More particularly the invention relates to a method for fractionating a solution by a chromatographic simulated moving bed (SMB) process in which the dissolved substances present in the feedstock are separated in the partial packed beds, and the formed separation profile is circulated more than once or less than once through the chromatographic separation loop during one cycle.

1. A method for fractionating a solution into at least two fractions by a chromatographic simulated moving bed (SMB) process, comprising:
 processing a solution in more than one cycle in at least one chromatographic separation loop comprising a chromatographic simulated moving bed (SMB) system having one or more columns containing chromatographic separation packing material resin beds comprising partial packed beds;  
 said solution comprising a feed solution comprising one or more of the following selected from the group consisting of a feedstock, a recycle liquid comprising a recycle fraction, liquid from a previous chromatographic separation loop, liquid from a subsequent loop, and a solution derived from any of the preceding;  
 forming at least one separation profile comprising a dry solids (DS) profile from said processing of said solution;  
 essentially filling packing material in said resin beds with said separation profile so that said resin beds are well utilized, said separation profile being narrow and said resin beds being long;  
 each cycle comprising a predetermined number of steps in a predetermined order, said steps comprising the following different phases selected from the group consisting of a feeding phase, a circulation phase, an eluting phase, and a recycling phase; at least some of the phases occurring sequentially, consecutively, simultaneously, concurrently, or continuously;  
 said feeding phase comprising feeding said solution into one of the columns and drawing and collecting a product, a residue comprising a residual fraction and/or other fraction from the SMB system;  
 said eluting phase comprising feeding an eluant into one or more columns and drawing and collecting the product, the residue comprising the residual fraction and/or other fraction from the SMB system;  
 said recycling phase comprising recycling said recycle liquid comprising said recycle fraction to at least one of the columns;  
 said circulation phase comprising circulating said solution with said dry solid (DS) profile through said columns of said loop while substantially preventing and without feeding further solution to said columns during said circulation phase and while substantially preventing and without drawing and collecting said products or fractions from the columns or loops of the SMB system during said circulation phase; and  
 said dry solids (DS) profile being circulated with said solution more than once through said columns of said loop during said cycle so that said separation profile passes through said chromatographic separation loop in said SMB system more than once during each cycle using said steps and phases.  
 
     
     
       2. A method according to  claim 1  wherein the separation profile is circulated through the columns of the chromatographic separation loop in the SMB system during each cycle, 1.5, 1.7, 2 or 3 times. 
     
     
       3. A method according to  claim 1  wherein:
 said eluting phase is different than and occurs simultaneously or at a different time than said recycling phase;  
 said eluting phase is different than and occurs simultaneously or at a different time than said feeding phase;  
 said circulation phase is different than and occurs simultaneously or at a different time than said feeding phase;  
 said circulation phase is different than and occurs simultaneously or at a different time than said eluting phase; and  
 said phases are used one or more times in one or more steps during each cycle.  
 
     
     
       4. A method according to  claim 1  wherein the feeding phase and recycling phase are carried out simultaneously or at a different time in one step, in one loop, in a column or in a part of a column. 
     
     
       5. A method according to  claim 1  wherein the simulated moving bed (SMB) process is sequential. 
     
     
       6. A method according to  claim 1  wherein the chromatographic separation system comprises two or more different loops, each loop comprising an SMB system separate and distinct from the SMB system of another loop. 
     
     
       7. A method according to  claim 1  wherein the chromatographic separation packing material bed is an ion exchange resin bed. 
     
     
       8. A method according to  claim 1  wherein the chromatographic separation packing material bed is a cation exchange resin bed. 
     
     
       9. A method according to  claim 1 , wherein the chromatographic separation packing material bed is a weakly acid cation exchange resin bed. 
     
     
       10. A method according to  claim 1 , wherein the chromatographic separation packing material bed is a strongly acid cation exchange resin bed. 
     
     
       11. A method according to  claim 1 , wherein the number of columns or chromatographic separation packing material beds are from 1 to 28. 
     
     
       12. A method according to  claim 1  wherein the number of steps is 1 to 50 during one cycle. 
     
     
       13. A method according to  claim 1  wherein the linear flow rate of said solution through said columns in said loop is 0.4 to 20 m/h. 
     
     
       14. A method according to  claim 1  wherein the solution to be processed comprises a liquid selected from the group consisting of: molasses, B-molasses, C-molasses, cane molasses, vinasse, fructose syrup, glucose syrups, beet-derived juices, invert sugar mixtures, stillage, starch hydrolysates, wood molasses, biomass molasses, wheat molasses, barley molasses, corn molasses, wood hydrolysates, milk whey solutions, lactose containing solution, lactulose-containing solutions, maltose-containing, solutions, maltitol-containing solutions, solutions containing amino acids, fermentation broths containing at least one organic acid, fermentation broths containing citric acid, fermentation broths containing organic acid, fermentation broths containing gluconic acid, bagasse hydrolysates, and solutions containing at least one of the following constituents of sucrose, betaine, carbohydrates, sugar alcohols, ionic substances, monosaccharides. disaccharides, pentose, xylose, rhamnose, arabinose, mannose, raffinose, inositol, mannitol, sorbitol, xylitol, erythritol, glutamic acid, glycerol, tagatose, isomaltulose, or trehalulose solutions. 
     
     
       15. A method according to  claim 14  wherein said wood molasses and said biomass molasses comprise xylan-derived material derived from vegetable material. 
     
     
       16. A method according to  claim 15  wherein said xylan derived material derived from vegetable matter is selected from the group consisting of: wood, wood chips, saw dust, hardwood, birch, aspen, beech, eucalyptus, poplar, alder, elm, softwood, grain, corn, wheat, barley, rice, oat, particulates of grain, straw, stems, hulls, husks, fibers, corn husks, barley husks, oat husks, rice hulls, corn fiber, corn stems, corn cobs, bagasse, almond shells, coconut shells, cotton seed bran, and cotton seed hulls. 
     
     
       17. A method according to  claim 14  wherein said biomass and wood molasses are obtained by acid hydrolysis or enzymatic hydrolysis of xylan. 
     
     
       18. A method according to  claim 14  wherein said biomass molasses comprises biomass hydrolysates derived from biomass. 
     
     
       19. A method according to  claim 14  wherein said biomass hydrolysates are obtained by a process selected from the group consisting of: direct acid hydrolysis of said biomass, enzymatic prehydrolysate of molasses obtained from steam exploded biomass or from by acetic acid or steam hydrolyzed biomass, acid hydrolysis of prehydrolyzate obtained from steam exploded biomass or from acetic acid or steam hydrolyzed biomass, and a sulphite pulping process. 
     
     
       20. A method according to  claim 14  wherein said wood molasses and said biomass hydrolysates are selected from the group consisting of: sulphite cooking liquor, spent sulphite pulping liquor, acid spent sulphite liquor, spent liquor from hardwood pulping, spent liquor from softwood pulping before hexoses are removed, spent liquor from softwood pulping after hexoses are removed, spent liquor from digestion of said biomass, spent liquor from hydrolysis of said biomass, spent liquor from solvent-based pulping, spent liquor from ethanol-based pulping, mother liquor from crystallization of xylose, diluted runoff of xylose crystallization from sulphite spent pulping liquor derived solution, waste solution from the paper industry, and waste solution from the pulping industry. 
     
     
       21. A method according to  claim 14  wherein said molasses is derived from spent liquor obtained by ultrafiltration or from a side removal during sulphite cooking. 
     
     
       22. A method according to  claim 14  wherein said molasses comprises a xylose solution. 
     
     
       23. A method according to  claim 1  wherein the solution to be fractionated is a sulphite cooking spent liquor. 
     
     
       24. A method according to  claim 1  wherein the solution to be fractionated is beet molasses. 
     
     
       25. A method according to  claim 1  wherein at least one product fraction withdrawn from the loop, said product fraction comprising at least one product selected from a group consisting of: glucose, fructose, sucrose, betaine, rhamnose, lactose, lactulose, maltose, maltitol, arabinose, mannose, raffinose, inositol, mannitol, glycerol, xylitol, xylose, sorbitol, erythritol, organic acids, amino acids, and glutamic acid. 
     
     
       26. A method according to  claim 1  wherein the cycle in the separation system comprises the following phases:
 a) said feeding phase wherein the feed solution is fed into one of the columns in one of the loops and optionally substantially simultaneously eluant is fed into the subsequent column, and a first product fraction and/or recycle fraction and a residue fraction are drawn and collected from the same or from the subsequent column;  
 b) said circulation phase, wherein liquid presenting the loop with its dry solids (DS) profile is circulated in the loop and simultaneously nothing is fed into or collected from the chromatographic separation loop;  
 c) said eluting phase, wherein eluant is fed into a column and residue fraction and optionally a second product fraction are drawn and collected from the same or from a subsequent column.  
 
     
     
       27. A method according to  claim 1  wherein said feed solution prior to feeding phase is subjected to at least one pretreatment process selected from the group consisting of: filtering, ultrafiltration, heating, concentrating, evaporation, neutralization, pH adjustment, volume adjustment, dilution, hydrogenation, softening by carbonation, and ion exchange. 
     
     
       28. A method according to  claim 1  wherein the feed solution comprises a dry solids (DS) content of 20% to 80% by weight on a dry solids (DS) basis. 
     
     
       29. The method according to  claim 1  wherein the number of columns or chromatographic separation packing material resin beds is from 2 to 12. 
     
     
       30. The method according to  claim 1  wherein the number of columns or chromatographic separation packing material resin beds is from 2 to 6. 
     
     
       31. A method according to  claim 1  wherein:
 the solution comprises sulphite cooking liquor comprising xylose, arabinose, glucose, galactose, rhamnose, mannose, and xylonic acid; and  
 at least one of the products comprises a xylose fraction having a greater percentage concentration by weight on a dry solids basis of xylose, arabinose, glucose, galactose, rhamnose, mannose, and xylonic acid, than in the feed solution.  
 
     
     
       32. A method according to  claim 1  wherein:
 the solution comprises xylose, arabinose, glucose, galactose, rhamnose, and mannose; and  
 at least one of the products comprises at greater percentage concentration by weight on a dry solids basis of xylose, arabinose, glucose, galactose, rhamnose, and mannose, than in the feed solution.  
 
     
     
       33. A method according to  claim 1  wherein:
 the solution comprises sucrose and betaine;  
 one of said fractions comprises a sucrose fraction having a greater percentage concentration by weight of sucrose on a dry solids basis than the sucrose in the feed solution; and  
 another of said fractions comprises a betaine fraction having a greater percentage concentration by weight of betaine on a dry solids basis than the betaine in the feed solution.  
 
     
     
       34. A method according to  claim 1  wherein:
 the solution comprises a fructose syrup comprising fructose; and  
 the product comprises a fructose fraction comprising a greater percentage concentration of fructose by weight on a dry solids basis than the fructose in the feed solution.  
 
     
     
       35. A method according to  claim 1  wherein:
 the solution comprises a maltose syrup comprising maltose; and  
 the product comprises a maltose fraction comprising a greater percentage concentration of maltose by weight on a dry solids basis than the maltose in the feed solution.  
 
     
     
       36. A method according to  claim 1  wherein the linear flow is 1 to 12 m/h. 
     
     
       37. A method for fractioning a solution into at least two fractions by a chromatographic simulated moving bed (SMB) process, comprising:
 processing a solution in more than one cycle in at least one chromatographic separation loop comprising a chromatographic simulated moving bed (SMB) system having one or more columns containing chromatographic separation packing material resin beds providing short resin beds comprising partial packed beds;  
 said solution comprising a feed solution comprising one or more of the following selected from the group consisting of a feedstock, a recycle liquid comprising a recycle fraction, liquid from a previous chromatographic separation loop, liquid from a subsequent loop, and a solution derived from any of the preceding;  
 forming at least one separation profile comprising a dry solids (DS) profile from said processing of said solution, said separation profile being long and broad;  
 essentially filling packing material in said short resin beds with said long and broad separation profile to well utilize said short resin beds;  
 each cycle comprising a predetermined number of steps in a predetermined order, said steps comprising the following different phases selected from the group consisting of a feeding phase, a circulation phase, an eluting phase, and a recycling phase; at least some of the phases occurring sequentially, consecutively, simultaneously, concurrently, or continuously;  
 said feeding phase comprising feeding said solution into one of the columns and drawing and collecting a product, a residue comprising a residual fraction, or other fraction from the SMB system;  
 said eluting phase comprising feeding an eluant into one or more columns and drawing and collecting the product, the residue comprising the residual fraction and/or other fraction from the SMB system;  
 said recycling phase comprising recycling said recycle liquid comprising said recycle fraction to at least one of the columns;  
 said circulation phase comprising circulating said solution with said dry solid (DS) profile through said columns of said loop while substantially preventing and without feeding further solution to said columns during said circulation phase and while substantially preventing and without drawing and collecting said products or fractions from the columns or loops of the SMB system during said circulation phase; and  
 said dry solids (DS) profile being circulated with said solution less than once through said columns of said loop during said cycle so that the separation profile passes less than once through said chromatographic separation loop in said SMB system during each cycle using said steps and phases.  
 
     
     
       38. A method claimed according to  claim 37  wherein at least some of said phases during said cycle occur sequentially, consecutively, simultaneously, concurrently, or continuously in the same or different loop. 
     
     
       39. A method claimed according to  claim 37  wherein:
 the processing occurs in at least two chromatographic separation loops comprising at least a first loop and a second loop, each loop comprising an SMB system and being separate and distinct from another loop, and each loop comprising one or more chromatographic beds, columns, or parts thereof separate and distinct from the other loop; and  
 a solution derived from one of the fractions drawn from the first loop is fractionated into at least two other fractions in the second loop.  
 
     
     
       40. A method claimed according to  claim 39  wherein at least some of the loops are connected in series with each other. 
     
     
       41. A method claimed according to  claim 39  wherein at least some of the loops are connected in parallel with each other. 
     
     
       42. A method claimed according to  claim 39  wherein the loops comprise closed loops, open loops, and combinations thereof. 
     
     
       43. A method according to  claim 42  wherein a solution, liquid, or fraction from one loop is transferred or passed to another loop when the loops are open. 
     
     
       44. A method claimed according to  claim 39  wherein the simulated moving bed (SMB) process in at least one of the loops comprises a sequential SMB process. 
     
     
       45. A method claimed according to  claim 39  wherein the simulated moving bed (SMB) process in at least one of the loops comprises a continuous SMB process. 
     
     
       46. A method according to  claim 39  wherein said product comprises a product fraction recovered from said first loop and/or said second loop. 
     
     
       47. A method according to  claim 39  wherein the pH of the feed solution in the first loop is the same or different than the pH of the solution in a second loop. 
     
     
       48. A method claimed according to  claim 37  wherein:
 said eluting phase is different than and occurs simultaneously or at a different time than said recycling phase;  
 said eluting phase is different than and occurs simultaneously or at a different time than said feeding phase;  
 said circulation phase is different than and occurs simultaneously or at a different time than said feeding phase;  
 said circulation phase is different than and occurs simultaneously or at a different time than said eluting phase; and  
 said phases are used one or more times in one or more steps during each cycle.  
 
     
     
       49. A method claimed according to  claim 37  wherein the solution to be processed comprises a liquid selected from the group consisting of: molasses, B-molasses, C-molasses, cane molasses, vinasse, fructose syrup, glucose syrups, beet-derived juices, invert sugar mixtures, stillage, starch hydrolysates, wood molasses, biomass molasses, wheat molasses, barley molasses, corn molasses, wood hydrolysates, milk whey solutions, lactulose-containing solutions, maltose-containing solutions, maltitol-containing solutions, solutions containing amino acids, fermentation broths containing at least one organic acid, fermentation broths containing citric acid, fermentation broths containing organic acid, fermentation broths containing gluconic acid, bagasse hydrolysates, and solutions containing at least one of the following constituents of sucrose, betaine, carbohydrates, sugar alcohols, ionic substances, monosaccharides, disaccharides, pentose, xylose, rhamnose, arabinose, mannose, raffinose, inositol, mannitol, sorbitol, xylitol, erythritol, glutamic acid, glycerol, tagatose, isomaltulose, or trehalulose solutions. 
     
     
       50. A method according to  claim 49  wherein said wood molasses and said biomass molasses comprise xylan-derived material derived from vegetable material. 
     
     
       51. A method according to  claim 50  wherein said xylan derived material derived from vegetable matter is selected from the group consisting of: wood, wood chips, saw dust, hardwood, birch, aspen, beech, eucalyptus, poplar, alder, elm, softwood, grain, corn, wheat, barley, rice, oat, particulates of grain, straw, stems, hulls, husks, fibers, corn husks, barley husks, oat husks, rice hulls, corn fiber, corn stems, corn cobs, bagasse, almond shells, coconut shells, cotton seed bran, and cotton seed hulls. 
     
     
       52. A method according to  claim 49  wherein said biomass and wood molasses are obtained by acid hydrolysis or enzymatic hydrolysis of xylan. 
     
     
       53. A method according to  claim 49  wherein said biomass molasses comprises biomass hydrolysates derived from biomass. 
     
     
       54. A method according to  claim 53  wherein said biomass hydrolysates are obtained by a process selected from the group consisting of: direct acid hydrolysis of said biomass, enzymatic prehydrolysate of molasses obtained from steam exploded biomass or from acetic acid or steam hydrolyzed biomass, acid hydrolysis of prehydrolyzate obtained from steam exploded biomass or from acetic acid or steam hydrolyzed biomass, and a sulphite pulping process. 
     
     
       55. A method according to  claim 49  wherein said wood molasses and said biomass hydrolysates are selected from the group consisting of: sulphite cooking liquor, spent sulphite pulping liquor, acid spent sulphite liquor, spent liquor from hardwood pulping, spent liquor from softwood pulping before hexoses are removed, spent liquor from softwood pulping after hexoses are removed, spent liquor from digestion of said biomass, spent liquor from hydrolysis of said biomass, spent liquor from solvent-based pulping, spent liquor from ethanol-based pulping, mother liquor from crystallization of xylose, diluted runoff of xylose crystallization from sulphite spent pulping liquor derived solution, waste solution from the paper industry, and waste solution from the pulping industry. 
     
     
       56. A method according to  claim 49  wherein said molasses is derived from spent liquor obtained by ultrafiltration or from a side removal during sulphite cooking. 
     
     
       57. A method according to  claim 49  wherein said molasses comprises a xylose solution. 
     
     
       58. A method according to  claim 49  wherein said feed solution is pretreated prior to the feeding phase in at least one pretreatment process selected from the group consisting of: filtering, ultrafiltration, heating, chromatography, concentrating, evaporation, neutralization, pH adjustment, volume adjustment, dilution, hydrogenation, softening by carbonation, and ion exchange. 
     
     
       59. A method claimed according to  claim 37  wherein liquid derived from said feed solution with its dry solids (dry substance) profile is partially circulated in at least one loop during each cycle for no more than a fraction selected from the group consisting of: (a) 0.5 circulations about the loop; (b) 0.7 circulations about the loop; or (c) 0.75 circulations about the loop. 
     
     
       60. A method claimed according to  claim 37  wherein there are at least more than one dry solids (dry substance (DS) profiles circulating simultaneously in the same loop during the circulation phase of each cycle. 
     
     
       61. A method claimed according to  claim 37  wherein the cycle starts at a different column as the previous cycle. 
     
     
       62. A method claimed according to  claim 37  wherein the location where the feed solution is fed in the feeding phase is advanced during processing compared to the previous cycle. 
     
     
       63. A method claimed according to  claim 26  wherein the location wherein the product or the fractions are drawn from the loop are shifted cyclically during processing. 
     
     
       64. A method claimed according to  claim 37  wherein eluent is fed into one location in the loop during the feeding phase and the feed solution is fed into a different location in the loop during the same feeding phase. 
     
     
       65. A method according to  claim 37  wherein each loop comprises a series of columns containing a cation exchange resin. 
     
     
       66. A method claimed according to  claim 37  wherein said phases can occur one or several times in different steps during each cycle. 
     
     
       67. A method according to  claim 37  wherein said feed solution is selected from the group consisting of: raw juice, diffusion juice, thin juice, thick juice, dilute juice, residual juice, molasses-containing liquid, and molasses-containing juice. 
     
     
       68. A method according to  claim 37  wherein said product comprises a product fraction comprising a sucrose fraction. 
     
     
       69. A method according to  claim 37  wherein said product comprises a product fraction comprising a xylose fraction. 
     
     
       70. A method according to  claim 37  wherein one of said fractions comprises a product fraction comprising a betaine fraction, and said betaine fraction comprises a greater percentage concentration of betaine by weight on a dry solids (dry substance) basis than at least one of said other fractions in or from said loops. 
     
     
       71. A method according to  claim 37  wherein said dry solids (dry substance) (DS) profile is advanced during said processing. 
     
     
       72. A method according to  claim 37  wherein said fractions are selected from the group consisting of one or more: sucrose fractions, betaine fractions, xylose fractions, residual fractions, and recycle fractions. 
     
     
       73. A method according to  claim 37  wherein said fractions comprise one or more compounds selected from the group consisting of: sucrose, betaine, xylose, arabinose, glucose, galactose, rhamnose, mannose, and xylonic acid. 
     
     
       74. A method according to  claim 37  wherein each loop contains at least one type of resin bed selected from the group consisting of: an ion exchange resin bed, a cation exchange resin bed, a weakly acid cation exchange resin bed, and a strong acid cation exchange resin bed. 
     
     
       75. A method according to  claim 74  wherein the composition of the resin beds in one loop is the same or different than the resin beds in another loop. 
     
     
       76. A method according to  claim 75  wherein one of the resin beds in one of said loops is in monovalent form and one of the resin beds in another one of said loops is in divalent form. 
     
     
       77. A method according to  claim 75  wherein a resin bed of the first loop has a different degree of cross linking than a resin bed of the second loop. 
     
     
       78. A method according to  claim 74  wherein the resin beds of the loops have similar or different particles sizes. 
     
     
       79. A method according to  claim 37  wherein said feed solution comprises components providing constituents comprising low migration rate constituents, intermediate migration rate constituents, and high migration rate constituents. 
     
     
       80. A method according to  claim 37  wherein said processing comprises one to 50 steps which are repeated until equilibrium is essentially achieved. 
     
     
       81. A method according to  claim 37  wherein said columns comprise 1 to 28 columns and said beds comprise 1 to 28 beds. 
     
     
       82. A method according to  claim 37  wherein said columns comprise 2 to 12 columns and said beds comprise 2 to 12 beds. 
     
     
       83. A method according to  claim 37  wherein said columns comprise 1 to 6 columns and said beds comprise 1 to 6 beds. 
     
     
       84. A method according to  claim 37  wherein the feed solution comprises a dry solids (DS) content of 20% to 80% by weight on a dry solids (DS) basis. 
     
     
       85. A method according to  claim 37  wherein:
 one of said fractions from the loop comprises sucrose;  
 the other fraction from one of the loops comprises a dissolved component selected from the group consisting of: betaine, inositol, raffinose, galactinol, serine, and amino acid.  
 
     
     
       86. A method according to  claim 37  wherein one of the fractions in the loop is selected form the group consisting of: a sucrose fraction, a by-product fraction, and a residue fraction. 
     
     
       87. A method according to  claim 37  wherein the product comprises at least one compound selected form the group consisting of: glucose, fructose, sucrose, betaine, rhamnose, arabinose, mannose, raffinose, lactose, lactulose, maltose, maltitol, inositol, mannitol, glycerol, xylitol, xylose, sorbitol, erythritol, organic acid, amino acid, and glutamic acid. 
     
     
       88. A method according to  claim 37  wherein:
 the feed solution comprises sulphite cooking liquor comprising xylose, glucose, galactose, rhamnose, mannose, and xylonic acid; and  
 at least one of the products comprises a xylose fraction having a greater percentage concentration by weight on a dry solids basis of xylose, glucose, galactose, rhamnose, mannose, and xylonic acid, than in the feed solution.  
 
     
     
       89. A method according to  claim 37  wherein:
 the feed solution comprises xylose, arabinose, glucose, galactose, rhamnose, and mannose; and  
 at least one of the products comprises at greater percentage concentration by weight on a dry solids basis of xylose, arabinose, glucose, galactose, rhamnose, and mannose, than in the feed solution.  
 
     
     
       90. A method according to  claim 37  wherein:
 the feed solution comprises sucrose and betaine;  
 one of said fractions comprises a sucrose fraction having a greater percentage concentration by weight of sucrose on a dry solids basis than the sucrose in the feed solution; and  
 another of said fractions comprises a betaine fraction having a greater percentage concentration by weight of betaine on a dry solids basis than the betaine in the feed solution.  
 
     
     
       91. A method according to  claim 37  wherein:
 the feed solution comprises a fructose syrup comprising fructose; and  
 the product comprises a fructose fraction comprising a greater percentage concentration of fructose by weight on a dry solids basis than the fructose in the feed solution.  
 
     
     
       92. A method according to  claim 37  wherein:
 the feed solution comprises a maltose syrup comprising maltose; and  
 the product comprises a maltose fraction comprising a greater percentage concentration of maltose by weight on a dry solids basis than the maltose in the feed solution.